A chemical sensor that detects chemicals using light emission due to a chemical bond has been studied. Specifically, if a probe material specifically bonding to a target material to be detected is adhered to the sensor and a sample is supplied to the sensor, a target material included in the sample bonds to the probe material. For example, by using a fluorescent label that can be introduced into a composite material of a target material and a probe material to cause the composite material to emit light, it is possible to detect the emitted light by a photoelectric conversion element. By causing a plurality of types of probe materials to be adhered to the sensor, it is also possible to specify the type of the target material included in the sample.
In such a chemical sensor, in order to perform the detection with high sensitivity and high accuracy, it is necessary to introduce only emitted light generated due to the bond between the target material and the probe material into the photoelectric conversion element and to eliminate light other than that, e.g., excitation light for generating fluorescent light.
For example, Patent Document 1 discloses a “biosensor with evanescent waveguide and integrated sensor” that uses an evanescent wave (near-field light) of excitation light to cause a sample to emit fluorescent light, similarly. The sensor has a configuration in which a detector, a filter, a contact cladding layer, and a waveguide layer are laminated in the stated order, and a sample is placed on the waveguide layer. It has a configuration in which excitation light (laser) is introduced into the waveguide layer in a direction parallel to the layer, and the detector detects the fluorescent light the fluorescent light from the sample that is excited with an evanescent wave leaked from the interface of the waveguide layer.
Moreover, Patent Document 2 discloses an “all polymer optical waveguide sensor” that uses an evanescent wave of excitation light to cause a sample to emit fluorescent light. The sensor has a configuration in which a polymer waveguide is formed on a polymer substrate, and a sample is fixed on the polymer substrate. The sample is excited with an evanescent wave of a light wave (coherent light) traveling through the polymer waveguide, and generates fluorescent light, which is detected by a detector.
In any of the inventions described in Patent Document 1 and Patent Document 2, the excitation light is confined in the waveguide structure to prevent the excitation light from reaching the photoelectric conversion element. Therefore, the evanescent wave for causing the sample fixed on the waveguide structure to emit fluorescent light is an element in both inventions.